SUMMARY

Box jellyfish, cubomedusae, possess an impressive total of 24 eyes of four
morphologically different types. Two of these eye types, called the upper and
lower lens eyes, are camera-type eyes with spherical fish-like lenses.
Compared with other cnidarians, cubomedusae also have an elaborate behavioral
repertoire, which seems to be predominantly visually guided. Still, positive
phototaxis is the only behavior described so far that is likely to be
correlated with the eyes. We have explored the obstacle avoidance response of
the Caribbean species Tripedalia cystophora and the Australian
species Chiropsella bronzie in a flow chamber. Our results show that
obstacle avoidance is visually guided. Avoidance behavior is triggered when
the obstacle takes up a certain angle in the visual field. The results do not
allow conclusions on whether color vision is involved but the strength of the
response had a tendency to follow the intensity contrast between the obstacle
and the surroundings (chamber walls). In the flow chamber Tripedalia
cystophora displayed a stronger obstacle avoidance response than
Chiropsella bronzie since they had less contact with the obstacles.
This seems to follow differences in their habitats.